feat: add New Policies Only filter toggle to policy browser

[atharrva01]

The policy library already badges recently added policies, but finding them meant scrolling through 640+ cards hunting for purple dots. This adds a New Policies toggle to the filter sidebar that narrows the grid to policies from the last 90 days (~166 currently).

It plays nicely with existing filters (severity, category, tags), shows up as a removable chip in the active filters bar, and clears with "Clear all". Wired up the existing isPolicyNew utility from utils.ts , it was already powering the badges, just never hooked into the browser itself.

Before

feature.2.before.3.mp4

After

feature.2.after.mp4

[welcome]

Thanks for opening your first Pull Request here! Please check out our Contributing guidelines and confirm that you Signed off.

[atharrva01]

hi @lucchmielowski I added a "New Policies" filter toggle that narrows the grid to last-90-day policies using the existing isPolicyNew utility.